The present invention relates to a mounting structure for a chemical injection tube for a geothermal well which is utilized to generate power from geothermal energy. The geothermal energy is contained in hot water and steam.
A considerable amount of alkaline earth metals is dissolved in geothermal fluid which is under high temperature and high pressure subterranean conditions. During fluid flow the alkaline metals tend to deposit onto wall surfaces of the well as carbonates which then adhere to the wall as scale.
The scale causes insufficient fluid production due to its plugging effect and, in extreme cases, the scale can completely close the well.
Furthermore, hot water in a deep subsurface formation can contain salt deposits depending upon the pressure, temperature, ion species ion concentration in the hot water.
There is no known method for providing a chemical injection tube in a geothermal well to prevent carbonate scale adhesion. A chemical injection method is known for hot spring wells. However, hot spring wells are generally so shallow compared to geothermal steam wells (hereafter called "geothermal wells"), that chemicals are injected by hand. Because geothermal wells are often deeper than 1000 m, manual chemical injection is difficult and dangerous due to high pressure hot steam.
It is possible to hang a chemical injection tube below the flashing point in a geothermal well, but the length of such tube can be more than 1000 m. Also, the weight would be 10 to 20 t, so a heavily loaded vertical pipe portion would have to be supported using a permanent hanger structure.
In addition, when the tube extends deep into the well there is a risk of corrosion or erosion, because it is always exposed to geothermal fluid which often includes gravel and dust.